simpleapp.java

derby数据库源码。。。。。。。。。。。。。

             *    // do something with the result set
             *  }
             * to process all returned rows, but we are only expecting two rows
             * this time, and want the verification code to be easy to
             * comprehend, so we use a different pattern.
             */

            int number; // street number retreived from the database
            boolean failure = false;
            if (!rs.next())
            {
                failure = true;
                reportFailure("No rows in ResultSet");
            }

            if ((number = rs.getInt(1)) != 300)
            {
                failure = true;
                reportFailure(
                        "Wrong row returned, expected num=300, got " + number);
            }

            if (!rs.next())
            {
                failure = true;
                reportFailure("Too few rows");
            }

            if ((number = rs.getInt(1)) != 1910)
            {
                failure = true;
                reportFailure(
                        "Wrong row returned, expected num=1910, got " + number);
            }

            if (rs.next())
            {
                failure = true;
                reportFailure("Too many rows");
            }

            if (!failure) {
                System.out.println("Verified the rows");
            }

            // delete the table
            s.execute("drop table location");
            System.out.println("Dropped table location");

            /*
               We commit the transaction. Any changes will be persisted to
               the database now.
             */
            conn.commit();
            System.out.println("Committed the transaction");

            /*
             * In embedded mode, an application should shut down the database.
             * If the application fails to shut down the database,
             * Derby will not perform a checkpoint when the JVM shuts down.
             * This means that it will take longer to boot (connect to) the
             * database the next time, because Derby needs to perform a recovery
             * operation.
             *
             * It is also possible to shut down the Derby system/engine, which
             * automatically shuts down all booted databases.
             *
             * Explicitly shutting down the database or the Derby engine with
             * the connection URL is preferred. This style of shutdown will
             * always throw an SQLException.
             *
             * Not shutting down when in a client environment, see method
             * Javadoc.
             */

            if (framework.equals("embedded"))
            {
                try
                {
                    // the shutdown=true attribute shuts down Derby
                    DriverManager.getConnection("jdbc:derby:;shutdown=true");

                    // To shut down a specific database only, but keeep the
                    // engine running (for example for connecting to other
                    // databases), specify a database in the connection URL:
                    //DriverManager.getConnection("jdbc:derby:" + dbName + ";shutdown=true");
                }
                catch (SQLException se)
                {
                    if (( (se.getErrorCode() == 50000)
                            && ("XJ015".equals(se.getSQLState()) ))) {
                        // we got the expected exception
                        System.out.println("Derby shut down normally");
                        // Note that for single database shutdown, the expected
                        // SQL state is "08006", and the error code is 45000.
                    } else {
                        // if the error code or SQLState is different, we have
                        // an unexpected exception (shutdown failed)
                        System.err.println("Derby did not shut down normally");
                        printSQLException(se);
                    }
                }
            }
        }
        catch (SQLException sqle)
        {
            printSQLException(sqle);
        } finally {
            // release all open resources to avoid unnecessary memory usage

            // ResultSet
            try {
                if (rs != null) {
                    rs.close();
                    rs = null;
                }
            } catch (SQLException sqle) {
                printSQLException(sqle);
            }

            // Statements and PreparedStatements
            int i = 0;
            while (!statements.isEmpty()) {
                // PreparedStatement extend Statement
                Statement st = (Statement)statements.remove(i);
                try {
                    if (st != null) {
                        st.close();
                        st = null;
                    }
                } catch (SQLException sqle) {
                    printSQLException(sqle);
                }
            }

            //Connection
            try {
                if (conn != null) {
                    conn.close();
                    conn = null;
                }
            } catch (SQLException sqle) {
                printSQLException(sqle);
            }
        }
    }

    /**
     * Loads the appropriate JDBC driver for this environment/framework. For
     * example, if we are in an embedded environment, we load Derby's
     * embedded Driver, <code>org.apache.derby.jdbc.EmbeddedDriver</code>.
     */
    private void loadDriver() {
        /*
         *  The JDBC driver is loaded by loading its class.
         *  If you are using JDBC 4.0 (Java SE 6) or newer, JDBC drivers may
         *  be automatically loaded, making this code optional.
         *
         *  In an embedded environment, this will also start up the Derby
         *  engine (though not any databases), since it is not already
         *  running. In a client environment, the Derby engine is being run
         *  by the network server framework.
         *
         *  In an embedded environment, any static Derby system properties
         *  must be set before loading the driver to take effect.
         */
        try {
            Class.forName(driver).newInstance();
            System.out.println("Loaded the appropriate driver");
        } catch (ClassNotFoundException cnfe) {
            System.err.println("\nUnable to load the JDBC driver " + driver);
            System.err.println("Please check your CLASSPATH.");
            cnfe.printStackTrace(System.err);
        } catch (InstantiationException ie) {
            System.err.println(
                        "\nUnable to instantiate the JDBC driver " + driver);
            ie.printStackTrace(System.err);
        } catch (IllegalAccessException iae) {
            System.err.println(
                        "\nNot allowed to access the JDBC driver " + driver);
            iae.printStackTrace(System.err);
        }
    }

    /**
     * Reports a data verification failure to System.err with the given message.
     *
     * @param message A message describing what failed.
     */
    private void reportFailure(String message) {
        System.err.println("\nData verification failed:");
        System.err.println('\t' + message);
    }

    /**
     * Prints details of an SQLException chain to <code>System.err</code>.
     * Details included are SQL State, Error code, Exception message.
     *
     * @param e the SQLException from which to print details.
     */
    public static void printSQLException(SQLException e)
    {
        // Unwraps the entire exception chain to unveil the real cause of the
        // Exception.
        while (e != null)
        {
            System.err.println("\n----- SQLException -----");
            System.err.println("  SQL State:  " + e.getSQLState());
            System.err.println("  Error Code: " + e.getErrorCode());
            System.err.println("  Message:    " + e.getMessage());
            // for stack traces, refer to derby.log or uncomment this:
            //e.printStackTrace(System.err);
            e = e.getNextException();
        }
    }

    /**
     * Parses the arguments given and sets the values of this class' instance
     * variables accordingly - that is which framework to use, the name of the
     * JDBC driver class, and which connection protocol protocol to use. The
     * protocol should be used as part of the JDBC URL when connecting to Derby.
     * <p>
     * If the argument is "embedded" or invalid, this method will not change
     * anything, meaning that the default values will be used.</p>
     * <p>
     * @param args JDBC connection framework, either "embedded", "derbyclient"
     *        or "jccjdbcclient". Only the first argument will be considered,
     *        the rest will be ignored.
     */
    private void parseArguments(String[] args)
    {
        if (args.length > 0) {
            if (args[0].equalsIgnoreCase("jccjdbcclient"))
            {
                framework = "jccjdbc";
                driver = "com.ibm.db2.jcc.DB2Driver";
                protocol = "jdbc:derby:net://localhost:1527/";
            }
            else if (args[0].equalsIgnoreCase("derbyclient"))
            {
                framework = "derbyclient";
                driver = "org.apache.derby.jdbc.ClientDriver";
                protocol = "jdbc:derby://localhost:1527/";
            }
        }
    }
}